BAL APD peeling from new plaster.

[GotWood]

Good evening all,

I am trying to tile a newly skimmed wall, but am having issues with the BAL APD primer peeling off after application. I would really appreciate our advice please.

Below is a summary of what has happened to date -

- I applied 2 neat coats (as per instructions) is came off as a skin.
- Suspecting it was over-polished I sanded it back and cleaned it of dust.
- Following advice I applied two coats of 1:1 dilute. It skinned again.
- I sanded back again and applied many coats of 1:6 dilute. Still no joy.

What am I doing wrong?!

My test to determine whether it is "skinned" it so apply a bit of tape and to pull it off. When I dod this it comes off easily with the primer attached to the tape. Other non-gypsum based surfaces I do this with does not have this issue, even when trying it with Duct tape.

All advice will be gratefuly received.

gw

 

[Richard C]

What size weight/tiles do you have & what adhesive do you plan to use?

edit;
how long did you leave between coats & before you did the test

 

[GotWood]

Hi Richard,

You may recognise this from another thread, but I thought I would start a new one as the other was a little off topic.

I will be tanking with WP1 and will use BAL Mosaic Fix (as advised by BAL tech help). The tiles are glass, 100x300mm and weigh 18kg/m2.

This peeling APD thing has baffled me completely. I am beginning to worry that hacking the plaster off is the only option; but this will wreck the place...

gw

 

[tpt]

what have bal said about this?

if its skinning over like that it would imply to me that the skim isnt porous - is it just standard finish plaster?

 

[Richard C]

You may recognise this from another thread, but I thought I would start a new one as the other was a little off topic.

So a link would be helpfull!

 

[GotWood]

Thank you for your replies.

Richard - not sure how you do a link but the address is: //www.diynot.com/forums/tiling/tiling-on-a-skim-devil-float-it.303358/#2216933

tpt - thistle multifinsh. I know I over polished it but have have sanded it back twice plus given it a going over with a wire brush (as per BAL tech advice). The plaster darkens when wet so water is clearly going in but leaving the APD on the surface.

Really annoying.

 

[Richard C]

When priming new plaster (which is not always necessary), it’s usual to prime & tile as soon as the primer is sufficiently dry, not leave it for 18 hours; the BAL Technical spec says “allow drying for 15-30 minutes before applying adhesive”. Letting PVA (not that you should ever use PVA when tiling) dry overnight before plaster skimming will also give similar & disastrous results with plaster adhesion. You seem to have tried several combinations, sanding & keying but still seem to be having problems, perhaps you’ve now sanded it too much. Over sanding plaster exposes the grain & this can make it course & very porous, perhaps it’s sucking the moisture from the primer before it has a chance to key. A trick I use for good paint adhesion over plaster is to apply 2/3 mist coats in quick succession, not letting them dry out in between; perhaps you could try one coat thinned 1:6 & a further two coats 1:1 but don’t leave it overnight before tiling. Only other thing I can think of is that you have some form of contamination in the plaster skim, did you add anything to the plaster when you mixed? Did you PVA over the plaster?

At 18 kg/sqm your over the maximum weight limit (20 kg/sqm) for plaster in sound condition once you factor in > 4 kg/sqm for the addy & grout (I assume your going to use powder adhesive?). There is undoubtedly a safety factor, possibly +10% but I’ve no idea really; it’s marginal.

 

[GotWood]

Very many thanks Richard.

The instructions on the APD state "Allow to dry thoroughly for 15-30mins before applying adhesive". I read this as meaning it will take up to 30 mins to dry.

I will do two test areas tonight -

1) Rough up further with a wire brush in case I have not broken through the polished surface yet;
2) On the existing surface apply 3 consecutive coats (1:6/1:1/1:1) and not allowing it to dry between each.

Is there any possibility that this 'skinning' is normal and fine to tile on?!

gw

 

[Richard C]

When I use primer, I’ve always tiled straight over it as soon as it’s dry, usually 30 minutes or so. I’ve never left it to dry overnight & then tried the Gaffa tape test on it, never had any reason to so I can’t really say.

 

[GotWood]

An update whch I would appreciate your comments on. I primed a few test patches varying the dilution of the primer and further roughing the surface up with a wire brush. The best result was multiple weak dilutions applied to the brushed area. So with this in mind I have done the whole wall, but I am still not entirely happy as it is still possible to remove the primer.

Richard - I found on another thread your advice for tiling over paint, you advised "To test the paint, stick an 18” length of 2” gaffa tape over the paint & pull it off quickly but steadily". With this in mind, why would a primer be any different?

Further to your reply above, as I need to tank, I cannot tile over the primer within 30mins of application.

 

[Richard C]

Richard - I found on another thread your advice for tiling over paint, you advised "To test the paint, stick an 18” length of 2” gaffa tape over the paint & pull it off quickly but steadily". With this in mind, why would a primer be any different?

The purpose of any primer is to prepare a surface for further treatment. Paint is not a tile primer, it will probably have been on the wall for many years & the original bond can be affected by all sorts of things such as moisture, UV light, nicotine etc. hence the need to test it’s bond strength. It also usual to score thoroiughly to provide a key through the paint onto the plaster below. Generally, primers should not be left to dry out completely but usually proceeding to the next stage before it’s fully set (although it may be touch dry) &, in some cases, while it’s still tacky.

Further to your reply above, as I need to tank, I cannot tile over the primer within 30mins of application.

No but you can tank over it; what product are you tanking with? Does it require a primer?

 

[GotWood]

Good evening Richard

I understand that it is not a tile primer, but if you check paint for it's bond strength, why not a primer? Afterall, they both form a layer between the adhesive and the substrate.

I am using BAL WP1 which comes with APD as part of the kit. Are there not times when you need a couple of days to complete a job so the primer completely dries out before you finish?

I will stick a tile up tonight and see how I get on. Is there a pro's tip to check that a tile has adhered properly, or do I just give it a good yank?

If the tile pulls away easily with a skin of primer attached, I will have to (whilst crying) take a chisel to the wall to remove the plaster and start again - I have tried everything else.

gw

 

[Richard C]

Good evening Richard

Good evening Gw

I understand that it is not a tile primer, but if you check paint for it's bond strength, why not a primer? Afterall, they both form a layer between the adhesive and the substrate.

I tried to explain that already, maybe you weren’t listening! Depending on what they are being used for, primers are designed to be either a reactive or passive agent between whatever you’re putting the primer onto & whatever you’re putting over the top. Your testing methods between each process are OTT & are not valid.

I am using BAL WP1 which comes with APD as part of the kit. Are there not times when you need a couple of days to complete a job so the primer completely dries out before you finish?

Not really, as a pro I can’t afford to & it’s never necessary if you use the right materials; but if it were, I would not prime! FFS Put the APD on & tank it in within 30 minutes.

I will stick a tile up tonight and see how I get on. Is there a pro's tip to check that a tile has adhered properly, or do I just give it a good yank? If the tile pulls away easily with a skin of primer attached, I will have to (whilst crying) take a chisel to the wall to remove the plaster and start again - I have tried everything else.

Your choice but it’s not a fair test of the materials you’re using. You’re attempting to prove every single stage of the process but you don’t really understand the purpose of priming. The tile will almost certainly come away pulling the primer & maybe the plaster skim with it. Do you realise that the recommendation before using any new installation in anger is 2 weeks!

Beginning to think I’m being trolled here as whatever advice I post gets questioned & knocked back. Myself & nobody I know of has had your problems with the products you’re using so either I’m missing something or you’re not listening & getting it wrong. Everyone else on here has long since given up & there is a limit to how many times I will bang my head against the wall so this is will be my last post so good luck with it but, to coin a well known phrase, I’m out!

 

[tictic]

In your first post you say .....newly skimmed plaster.......how long as it been on the wall...??....

 

[GotWood]

Richard, I am very sorry if I have given the impression that I am ungrateful for the advice, this is not the case and I thank you for the time you have spent in replying to me.

I was just looking for clarity on your use of primers as you advise to tile on it 30mins after application / not to let it dry out completely, whilst the BAL application instructions advise to leave it to "dry thoroughly". Clearly you have a lot of experience to fall back on which is why I value your time.

Should anyone else be following this, any tips/ideas would be appreciated.

gw